[LibWhacker]

Yep, I was combining those two equations. Thanks, doc. Thwarted again, LOL! :-)

Question: But can't we envision being an observer photon moving alongside another photon?

[Physicist]

But can't we envision being an observer photon moving alongside another photon?

The use of the word "observer" implies a vantage point (i.e., an inertial frame).